How to properly replace bearings in RC Heli Xtreme
Today were going to talk about the proper use of thrust bearings for the Xtreme framed V120's.
In case nobody was aware nearly all larger helis use a combination of radial bearings and thrust bearings in the head support. There are plenty of good reasons for this besides the fact that it's the mechanically correct method for reducing friction on a helicopter head.
I decided that the standard issued radial bearings that my Xtreme frame came with weren't doing the best possible job of reducing friction. This was evidenced with the fact that if I over- tightened the collar just a hair it would bind the radial bearings up big time. It made no difference if the tail gear was on or not so this wasn't caused by a gear mesh problem.
This apparent binding, due to side axial loading a radial bearing, is what happens every time you use pitch in either direction. Placing high axial loads on radial bearings is mechanically incorrect, IMO this can lead to premature bearing ware and lots extra friction.
This isn't something you want on a micro heli that has very limited battery and motor power. As a result of using incorrect bearings you can expect to see wasted power with reduced run times, premature motor and bearing ware, unsmooth operation, increased bogging during pitch maneuvers, and higher temps of both the battery and the motor will occur.
Luckily the Xtreme frame was designed to use both radial bearings and a thrust bearing at each end of the head support. It was too expensive to implement this design feature using the expensive bearings so they cut corners on the final production run. They originally used cheap radial and thrust bearings but they had issues, mostly just because of the lower quality.
Fortunately they had the dimensions correct to allow the use of 2x5x2.3 radial bearings along with the 2x6x3 thrust bearings.
I just had to type in the required size, metric series 2x6x3 and scroll down for the thrust bearing, you will see them part # F2-6.
Same for the inner radial bearings 2x5x2.3, I'm using the 440C ones part# SMR682-ZZC#3.
I can tell you that the difference is night and day, no comparison at all. The radial thrust bearing combo is so much smoother I can't believe it. There is also zero play in this system and obviously much less friction.
You pay for what you get here, these boca bearing are over ten bucks each. It was well worth the money in my case. But this did bring the total for the Xtreme frame up to nearly 90 dollars.
It's no wonder they couldn't implement this into production, it's just too expensive "to do it the right way".
These pictures show the thrust bearing and the incorrect size 2.5mm wide radial bearing. The correct size for the radial bearing width is 2.3mm. This width allowed for perfect gear mesh as well. Everything just fit right in like it was originally designed that way,...which it was.
(originally written on RCGroups by chevell)